Chapter 1: Problem 67
If \(y\) is a linear function of \(x,\) then the ratio \(y / x\) is constant for all points on the graph at which \(x \neq 0\)
Short Answer
Expert verified
The ratio \( y/x \) is constant only if the function is of the form \( y = mx \) (i.e., \( c = 0 \)).
Step by step solution
01
Define a Linear Function
A linear function is typically defined as \[ y = mx + c \]where \( m \) is the slope and \( c \) is the y-intercept.
02
Express the Ratio y/x
For a linear function of the form \( y = mx + c \), express the ratio \( \frac{y}{x} \) as \[ \frac{y}{x} = \frac{mx + c}{x} \]. This simplifies to \[ \frac{y}{x} = m + \frac{c}{x} \].
03
Consider Cases where x ≠0
To determine when \( \frac{y}{x} \) is constant, observe the expression \( m + \frac{c}{x} \). For the ratio to remain constant for all \( x eq 0 \), the term \( \frac{c}{x} \) should not change with \( x \), which occurs only if \( c = 0 \).
04
Conclusion on Linearity and Constant Ratio
If \( c = 0 \), then our function becomes \( y = mx \), and \( \frac{y}{x} = m \), which is indeed constant. For a general linear function \( y = mx + c \) with non-zero \( c \), \( \frac{y}{x} \) is not constant as depends on \( x \). Thus, for \( \frac{y}{x} \) to be constant for all points \( x eq 0 \), the linear function must be of the form \( y = mx \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope
The slope of a linear function is a crucial concept to understand the graph of the function. Imagine the slope as a measure of how steep a line is on a graph. It tells us how much the value of \( y \) changes for every increase of 1 unit in \( x \). The formula for a linear function is given by \( y = mx + c \), where \( m \) represents the slope.
- If \( m \) is positive, the line rises as it moves from left to right.
- If \( m \) is negative, the line falls as it moves from left to right.
- If \( m \) equals zero, the line is completely horizontal, indicating no change in \( y \) as \( x \) changes.
y-intercept
The y-intercept is another important element in the equation of a linear function \( y = mx + c \). The y-intercept, represented by \( c \), tells us where the line crosses the y-axis.
- This intersection point occurs when \( x = 0 \).
- The value of \( c \) gives the starting position of the line on the y-axis.
Constant Ratio
When dealing with linear functions, the term "constant ratio" refers to the condition where the ratio of \( y \) to \( x \), expressed as \( \frac{y}{x} \), remains the same across all points on the graph.
- If \( c = 0 \), the function becomes \( y = mx \), making \( \frac{y}{x} = m \) a constant.
- This constant nature implies that the relationship between \( y \) and \( x \) is directly proportional.
x not equal to zero
In the context of linear functions, the condition \( x eq 0 \) is critical for the analysis of the ratio \( \frac{y}{x} \). When \( x = 0 \), you potentially face undefined expressions in mathematics since you can’t divide by zero.
- Thus, the condition \( x eq 0 \) prevents this problem, ensuring the expression \( \frac{y}{x} = m + \frac{c}{x} \) is well-defined.
- This condition is crucial for verifying if the ratio of \( \frac{y}{x} \) remains constant.